1. Field of the Invention
The present invention relates to a communication system and a communication method thereof. More particularly, the communication system of the present invention comprises a base station (BS), a femtocell and a core network. When the core network determines that a voice data transmission service is about to be provided to a user equipment (UE), the core network enables the BS to establish a wireless connection with the femtocell so as to perform a voice data transmission with the UE via the wireless connection.
2. Descriptions of the Related Art
The advancement of the communication industry has made it possible to provide users with a higher communication quality. For residential or small business environments, femtocells have been deployed as a supplement to original base stations (BSs) by the communication service provider to ease the burden of the BSs so that the overall signal coverage, the data transmission rate and the network capacity of the communication network can be improved. The femtocells are connected to a core network of the communication service provider via an Internet Service Provider (ISP) network such as a digital subscriber line (DSL) network or a cable modem network.
However, because the data transmission between the femtocells and the core network must be accomplished through the ISP network, the quality of service (QoS) of the femtocells is determined also by the network quality of the ISP network. The QoS of the femtocells and, especially, the QoS of voice data transmission tends to degrade at peak hours (i.e., time periods when the overall network traffic is relatively high) of the ISP network. Usually, the degradation of the QoS of voice data transmissions is the most obvious for the user, so once a user fails to normally make a phone call via the femtocell, the willingness of the user to use a femtocell is greatly discouraged.
Accordingly, an urgent need exists in the art to provide a solution capable of preventing the QoS of voice data transmissions provided by the femtocells from being influenced by the network quality of the ISP network.